I also see the same behavior.
A way to turn off building before debugging could be very important.
I need to debug a tagged version of my software and I don't want to rebuild it: I want to debug it as is!!
In "Debug configuration" => "Program" => "Program" is written "${build_artifact:D135B_P30}" where D135B_P30 is the binary name produced by the build.
Could be this setting to rebuild before debugging?